Method of removing fatty acid coating from hematite concentrate



United States Patent 1 3,441,401 METHOD OF REMOVING FATTY ACID COATINGFROM HEMATITE CONCENTRATE Rodney L. Stone, Allentown, and William M.Aubrey, Jr.,

Bethlehem, Pa., assignors to Bethlehem Steel Corporation, a corporationof Delaware No Drawing. Filed Oct. 26, 1966, Ser. No. 589,513 Int. Cl.C211) 1/14; B03c 1/00; B0311 1/10 US. Cl. 75-5 4 Claims This inventionrelates in general to a method of preparing, pelletizing and induratingiron ores containing magnetite and hematite.

It is well known in the art that low grade magnetite iron orescontaining hematite may be upgraded by separating the hematite andgangue particles from the magnetite particles by magnetic separation.The hematite particles are then separated from the gangue material byfroth-floatation in which the hematite particles are coated with a fattyacid collector reagent, for example, oleic, linoleic or linolenic acid,and removed from the frothflotation cells as the float product. Thegangue material is not coated and sinks to the bottom of the cells andis removed as the sink product.

Unfortunately, the fatty acid collector which coats the hematiteconcentrate is tenacious and is diflicult to remove by conventionalmethods from the hematite concentrate, As a result, when pellets madefrom such concentrates or from mixtures of such concentrates withmagnetite concentrates, and containing as little as 2% hematite, aresubjected to rapid heating to high temperatures, for example 2300 F. to2400" F., during the induration step, they tend to explode or spall. Asa result, it has not been possible heretofore to pelletize and induratehematite concentrates recovered by the froth-floatation method abovedescribed in a shaft furnace and only with difliculty in a grate-typefurnace.

It is therefore, the object of this invention to provide a method ofremoving the fatty acid coating from hematite concentrate, therebymaking it possible to utilize anionic floation as an economical methodof recovering hematite concentrates which can be satisfactorily pelletized and indurated.

Broadly, the invention includes subjecting a low grade siliceousmagnetite ore which contains hematite to magnetic separation for removalof the magnetite concentrate, treating the magnet tailings from saidmagnetic separation by froth flotation for recovery of the hematite,treating the hematite concentrate with leonardite, mixing the magnetiteconcentrate and treated hematite concentrate, filtering the mixture andthen pelletizing and indurating pellets formed from the filteredmagnetite-hematite mixture.

In a more detailed description of the invention, medium and low gradesiliceous magnetite ore which contains hematite,.pyrite, apatite, iscrushed and Wet ground to a relatively fine size which is suitable forseparation of the magnetite concentrate from the hematite concentrateand siliceous gangue by magnetic separation. The magnetite concentratenow is of a fineness suitable for pelletizing, for example a specificsurface area of between 1200 cm. gram and 1500 cm. gram.

The non-magnetic slurry from the magnetic separators contains hematite,siliceous gangue, pyrite and apatite. The slurry is treated inconventional manner in frothflotation cells to remove the pyrite. Theslurry is then deslimed and again treated in a conventional manner infroth-flotation cells to remove the apatite. The slurry which nowcontains hematite and siliceous gangue is thickened and passed tofroth-flotation cells wherein an anionic fatty acid collector forexample oleic, linoleic or linolenic acid is added to the slurry. Thefatty acid collector coats "ice the hematite concentrate thereby causingit to float and pass out of the froth-flotation cells as the floatportion. The siliceous gangue is not coated by the fatty acid collectorand sinks in the froth-flotation cells and is removed therefrom as thesink portion.

The hematite concentrate is too coarse for pelletizing at this stage andmust be ground to a suitable fineness, for example such that thespecific surface area of the concentrate is between about 1200 cm. /gramand 1500 cm. gram.

We have found that by adding a mineral, leonardite, to the hematiteconcentrate during such grinding thereof, the fatty acid collector isremoved from the hematite concentrate thereby making it possible to mixthe hematite concentrate with the magnetite concentrate to form pelletswhich may be indurated without danger of exploding or spalling in theindurating furnace. Leonardite is a dark brown earthy type friable solidwhich is though to be a derivative of lignite and has a high content ofoxygen.

The amount of leonardite so added may be as little as 45 pounds per tonof hematite concentrate. It is preferred, however, to use about 50pounds of leonardite per ton of hematite concentrate.

The slurry of hematite concentrate and leonardite from the grinding millis mixed with the ground magnetite concentrate. The mixture is thenfiltered to reduce the moisture in the concentrate to the degreenecessary for satisfactory balling, for example 8% to 10% moisture. Themagnetitehematite concentrate remains in the filter as filter cake andsubstantially all of the leonardite passes through the filter with thewater. The magnetite-hematite concentrate is then pelletized. Ifdesired, a binder such as 0.6% bentonite may be added to the concentratefor pelletizing. The pellets are indurated in a suitable furnace atsuitable temperatures for example about 2100 F. to about 2400 Fpreferably temperatures approaching 2400 F.

In a specific example of the invention, 320 tons per hour of a siliceousmagnetite-hematite ore were ground to a fineness such that to of the orepassed through a 325 mesh screen. This ground ore was further processedby magnetic separation to remove the magnetite concentrate at a rate of270 tons per hour from the hematite and siliceous gangue. The magnettailing slurry containing the hematite and siliceous gangue was then fedto a pyrite flotation circuit and an apatite flotation circuit whereabout 2.4 tons per hour of pyrite concentrate and about 7.1 tons perhour of apatite concentrate were removed from the slurry. About 0.03pound of sulfuric acid and 0.1 to 0.2 pound of a refined fatty acidcollector (oleic acid) were added to the slurry in the finalfrothflotation cells The flotation pH was about 6.0. Approximately 20tons per hour of hematite concentrate containing about 64.0% iron, wasrecovered as the float product, while 9.0 tons per hour of siliceousgangue was removed as the sink product. The slurry of hematiteconcentrate was then charged at the rate of about 5 tons per hour to agrinding mill. Leonardite was added to the hematite concentrates in thegrinding mill in amounts varying from 45 pounds to pounds per ton ofsuch concentrates. It was found that 45 pounds of leonardite per ton ofhematite concentrate was sufficient to remove substantially all thefatty acid collector from the concentrate. During grinding the size ofthe hematite concentrate was reduced from a specific surface area ofabout 650 cm. /gram to a specific surface area suitable for pelletizingor about 1400 cm. /gram. The magnetite concentrate which had been groundto a size suitable for pelletizing namely about 1400 cm?/ gram was mixedwith the slurry of hematite concentrate and leonardite and passed to afilter where a portion of the water and substantially all the leonarditewere removed from the slurry, The filtered magnetiteconcentrate-hematite concentrate was then formed into pellets of about0.50" in diameter. The pellets Were indurated at 2350 F. in a verticalshaft furnace. No problems with exploding or 5 spalling pellets wereencountered.

We claim:

1. A method of producing indurated pellets of magnetite-hematiteconcentrate recovered from a low grade magnetite ore containinghematite, pyrite, silica and apatite comprising:

(a) Wet grinding the ore to a fineness suitable for magnetic separation,(b) magnetically separating the magnetite concentrate from thesiliceous-bearing hematite,

(c) adding an anionic fatty acid collector to the slurry and removingthe hematite concentrate as a float product from the siliceous gangue,

(d) grinding the hematite concentrate slurry to a fineness suitable forpelletizing,

(e) adding not less than pounds of leonardite per ton of hematiteconcentrate during the grinding thereof,

(f) mixing the recovered magnetite concentrate with the leonardite andhematite concentrate slurry, 2

(g) filtering the magnetite concentrate-leonarditehematite concentrateslurry to remove substantially all the leonardite therefrom,

(h) pelletizing the magnetite-hematite concentrate,

and 30 (i) indurating the pellets.

2. A method as claimed in claim 1 in Which the specific surface area ofthe hematite concentrate of step (d) is within the range of 1200cmF/gram to about 1500 cmI /gram.

3. A method as claimed in claim 1 in which the amount of leonarditeadded in step (e) is from about pounds to about 90 pounds per ton ofhematite concentrate.

4. A method as claimed in claim 1 in which the temperature of step (i)is about 2100 F. to about 2400 F.

References Cited UNITED STATES PATENTS 5 L DEWAYNE RUTLEDGE, PrimaryExaminer.

E. L. WEISE, Assistant Examiner.

US. Cl. X.R.

1. A METHOD OF PRODUCING INDURATED PELLETS OF MAGNETITE-HEMATITECONCENTRATE REVOVERED FROM A LOW GRADE MAGNETITE ORE CONTAININGHEMATITE, PYRITE, SILICA AND APATITE COMPRISING: (A) WET GRINDING THEORE TO A FINENESS SUITABLE FOR MAGNETIC SEPARATION, (B) MAGNETICALLYSEPARATING THE MAGNETITE CONCENTRATE FROM THE SILICEOUS-BEARINGHEMATITE, (C) ADDING AN ANIONIC FATTY ACID COLLECTOR TO THE SLURRY ANDREMOVING THE HEMATITE CONCENTRATE AS A "FLOAT" PRODUCT FROM THESILICEOUS GANGUE, (D) GRINDING THE HEMATITE CONCENTRATE SLURRY TO AFINENESS SUITABLE FOR PELLETIZING, (E) ADDING NOT LESS THAN 45 POUNDS OFLEONARDITE PER TON OF HEMATITE CONCENTRATE DURING THE GRINDING THEREOF,(F) MIXING THE RECOVERED MAGNETITE CONCENTRATE WITH THE LEONARDITE ANDHEMATITE CONCENTRATE SLURRY, (G) FILTERING THE MAGNETITECONCENTRATE-LEONARDITEHEMATITE CONCENTRATE SLURRY TO REMOVESUBSTANTIALLY ALL THE LEONARDITE THEREFROM, (H) PELLETIZING THEMAGNETITE-HEMATITE CONCENTRATE, AND (I) INDURATING THE PELLETS.